Microtome

ABSTRACT

A small and simple portable microtome has a base with means either for holding a paraffin embedded specimen or freezing and securing a specimen for immediate sectioning by a cutting head which is mounted upon a vertical metering post for cutting in a horizontal plane. The post is threaded into the base and has a metering wheel for adjustment of the thickness of the section to be taken. Latches anchored respectively to the base and cutting head cooperate with the metering wheel to determine cutting operation and product.

United States Patent [1 1 Darbo [4 1 Sept. 2, 1975 MICROTOME [76]Inventor: Rolf E. Darbo, PO. Box 2158,

Madison, Wis. 53701 [22] Filed: Apr. 3, 1974 21 Appl. No.: 457,469

[52] US. Cl. 83/170; 83/592; 83/9155 [51] Int. Cl. B26D 5/10; B26D 7/08[58] Field of Search 83/170, 915.5, 573, 592, 83/584, 608

[56] References Cited UNITED STATES PATENTS 2,292,973 8/1942 Richards83/9155 X 2,984,007 5/1961 Lundin r 83/608 3,496,819 2/1970 Blum r83/608 X 3,799,029 3/1974 Cole et a1. 83/9155 X Primary ExaminerWil1ieG. Abercrombie Attorney, Agent, or FirmDarbo, Robertson & Vandenburgh 57 ABSTRACT A small and simple portable microtome has a base with meanseither for holding a paraffin embedded specimen or freezing and securinga specimen for immediate sectioning by a cutting head which is mountedupon a vertical metering post for cutting in a horizontal plane. Thepost is threaded into the base and has a metering wheel for adjustmentof the thickness of the section to be taken.'Latches anchoredrespectively to the base and cutting head cooperate with the meteringwheel to determine cutting operation and product.

5 Claims, 9 Drawing Figures PATENTED SEP 2 I975 SHEET 1 UP 2 MICROTOMEBACKGROUND AND SUMMARY OF THE INVENTION In alternate procedures forcutting extremely thin slices from specimen portions of organicmaterials, such as woody plant growth or animal (including human)tissues, for subsequent microscopic examination, the specimen may beembedded in a block of paraffin to hold it for cutting or may be frozento render it solid and held firmly for the accurate cutting of a thinslice. Each technique has its advantages and both are in current usealthough the freezing technique is generally to be preferred in theexamination of animal tissue.

Microtome apparatus heretofore available has been complicated, veryexpensive and usually too large to be considered portable. The specimenis frequently prepared in a separate apparatus for the sectioningoperation in the mierotome, whether it is to be embedded in paraffin orfrozen. The specimens are usually very small and the separation of thefreezing and slicing operations present problems, such as prematurethawing of the specimen, which are difficult to overcome.

The object of the present invention is to provide a combined mierotomeunit wherein the base embodies means for concurrently freezing andsecuring the frozen sample in position for cutting and also, if desired,means for securing a specimen embedded in paraffin for cutting. Afurther object is to provide such a microtome unit which is highlyversatile in use, being capable of cutting sections of desired thicknessin a wide range and of cutting a succession of sections without thenecessity of adjustment between cuts.

Further and important objects are to provide an extremely simple andtherefore inexpensive and a very small and therefore highly portablecombination freezing and cutting mierotome unit.

Other features of the mierotome apparatus will be come apparent from thefollowing description in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective view of the mierotome unit including a clamp forsecuring the unit to a work surface;

FIG. 2 is a plan view of the unit of FIG. 1;

FIG. 3 is a longitudinal view of the unit in vertical cross section;

FIG. 4 is a cross-sectional view taken at the line 4 4 of FIG. 2;

FIG. 5 is a perspective view of the base-anchored metering wheel latch;

FIG. 6 is a perspective view of the internally threaded meteringbushing;

FIG. 7 is a perspective view of the cutting headanchored metering wheellatch;

FIG. 8 is a detail view showing the cutting blade support with the bladeturned over for a steeper cutting angle. and

FIG. 9 is a cross-sectional view showing an alternative construction ofthe cutting head.

DESCRIPTION OF SPECIFIC EMBODIMENTS The base I of the mierotome unitshould be made from a material having a low coefficient of thermalconductivity. It may advantageously be injection molded from a plasticmaterial such as, for example,

(ill

polycarbonate resin, to form a rigid structure. The cutting headassembly 2 is mounted in the base for rotation about a vertical axis.Base 1 contains means for freez ing and securing a specimen in positionfor cutting and forsecuring a paraffin-embedded specimen for cutting.

It also contains and carries metering elements for cooperation withcutting head metering elements to determine the level at which the cutswill be taken and therefore the thicknesses of the sections.

The cutting head contains structure for holding the cutting blade andfor accurately guiding the movement of the blade in cutting the section.

Metering post 3 serves as the support for cutting head assembly 2. Thelower portion 4 of the metering post is threaded to screw into thecorrespondingly threaded metering bushings 5 which is mounted in avertical well provided for the purpose at the middle of base 1. Ametering wheel 6 having circumferential notches 7 is affixed to post 3and a conical shoulder support 8 is either affixed to or formed as anintegral part of post 3.

Blade holder 9, which may also advantageously be injection molded fromplastic, has a conical interior adapted to seat upon conical shouldersupport 8. An arm 10 to which the cutting blade 11 is removably secured,extends radially from and at right angles to the axis of the hub portionof the blade holder 9. For ease in tolerance maintenance and smootheroperation, the conical shoulder support 8 is preferably formed with topand bottom frustro-conical sections 8a and 8b for engagement with theconical inner surface of the hub portion of blade holder 9.

To complete the cutting head assembly, a compres' sion spring 12 isarranged between a washer l3 and a knurled hand nut 14 which is screwedonto the top portion of post 3 sufficiently to compress spring 12 andprovide frictional engagement between washer l3 and the top of the hubportion of blade holder 9 and between the conical surfaces of theconical shoulder support 8 and the interior of the cutting head hub.

As is best seen in FIGS. 3 and 6, the internally threaded meteringbushing 5 is firmly held in vertical position at approximately themiddle of the mierotome base. The bushing is slotted throughout itslength. This slot 15 provides clearance so that the bushing may be keptin firm engagement with the threaded lower portion 4 of metering post 3by means of set screw 16 which also serves to hold the bushing firmly inplace. By adjusting the set screw, wobbling of the metering post in thebushing can be prevented and, at the same time, the desired degree offrictional gripping of the post by the bushing may be established andmaintained.

Rectangular cavity 17 is provided; at one end of mierotome base 1 forthe reception of a block-of paraffin in which a specimen to be sectionedis embedded (or other solid specimen, such as wood, bone, woodyvegetable matter. etc. Set screws ll8 are provided for holding theparaffin block firmly in the position desired for slicing a section fromthe top of the specimen.

At the other end of the base 1. means are provided for freezing andmounting a specimen. The horizontal surface 19 of specimen freezingstage 20 is provided to receive the unfrozen specimen and, afterrefrigeration of the freezing stage. to hold the specimen which isfrozen to the surface securely in position for sectioning. Thecylindrical flange 21 which is an integral part of the freezing stageextends down into the well 22 in the base of the mierotome. The purposeof the flange is to support the freezing stage and also to provide arelatively large area of heat exchange surface for the rapid cooling ofthe freezing stage when refrigerant is supplied to it. A milled shoulder23 is provided for mounting the stage in well 22 and also permits carbondioxide gas to escape while trapping the snow. A refrigerant nozzlesocket 24 is screwed into the threaded surface of flange 21. Holes 25permit the passage of refrigerant introduced through socket 24 forcirculation over the exterior as well as interior surfaces of flange 2]and of the freezing stage.

The freezing stage 20 is made sufficiently massive to serve as a thermalreservoir to keep the specimen frozen for a reasonable period of timeafter the refrigerant supply is discontinued.

Othe parts and structural features will be described in connection withthe description of the manner of use of the combined microtome unit.

If the specimen to be sectioned is to be frozen it is placed upon thesurface 19 of the freezing stage 20 with the portion to be sliced offuppermost. A suitable refrigerant, such as carbon dioxide in liquidstate, is then introduced from a supply container, not shown, through acontact nozzle such as that indicated at 26, through socket 24. Forportability, a one shot capsule may be used in which case therefrigerant is introduced through channel 35 by means of a hypodermicneedle attachment introduced downwardly through the top of the channel.The specimen is cooled by transfer of heat to the freezing stage as thelatter is cooled until the specimen is frozen and frozen to surface 19.It is then ready for the cutting operation. Since some materials slicebest at certain temperatures, provision is made at 20a for insertion ofa suitable thermistor to measure the temperature of the freezing stage.

To cut a slice from the top of the frozen specimen, the metering post 3is first screwed down into metering bushing 5, either by rotating theentire cutting head assembly 2 or by turning the post by means of theknurled hand nut 14, until the cutting edge of the blade is at the levelof the top of the frozen specimen. If sections equal to the distancebetween the screw threads of the metering bushing are desired, eachsuccessive turn of the cutting head assembly will cut a slice of thisthickness from the specimen. For example, if the distance betweenthreads is one sixty-fourth, inch, the thickness of each slice will beone sixty-fourth inch. If, however, the thinnest possible slice is to becut from the specimen, the head assembly or metering post and wheel 6may be rotated through the angular distance of only one notch 7 and themetering wheel then locked into position with respect to the base bymeans of latch 27 which, as is best shown in FIGS. 1 and 5, is mountedfor vertical movement in base 1 to engage stop 28 with or disengage stop28 from a notch 7. Latch 27 slides and is retained in an L-shapcd groove29 (FIG. 2) and has a leaf spring element 30 to frictionally hold thelatch in the groove and handle tabs 31 for the manual manipulation ofthe latch.

With the metering wheel 6 locked in stationary position by latch 27,rotation of blade holder 9 about metering post 3 carries the cuttingedge of the blade around and over the specimen in a plane normal to theaxis of the metering post. If, after the top slice has been cut from thespecimen, another slice of minimum thickness is desired, latch 27 iswithdrawn and the cutting head assembly turned down one notch and againlocked into stationary position by the latch. Rotation of the bladeholder will then effect the taking of another section of minimumthickness from the specimen. If somewhat thicker slices are desired, thecutting head assembly may be turned two or more notches to double, etc.,the thickness of the section taken.

In the microtomc unit shown by way of example, the threads of themetering post and bushing are one sixtyfourth inch apart and themetering wheel is provided with forty notches equally spaced apart. Thethinnest section that may be taken by advancing the metering wheel onenotch is 12 microns. The capability of producing thinner sections may beincreased by providing a finer thread and/or a larger number of notcheson the metering wheel. Means may also be provided for locking themetering wheel at positions intermediate adjacent notches. v

A latch 32 is pivotally mounted upon blade holder 9 by means of screw 33to lock the blade holder to the metering wheel by engagement of latchstop 34 with a notch 7. With the metering wheel so locked to the bladeholder, the blade holder may be driven in rotation by manual forceapplied to the knurled hand nut 14 or the metering post 3 may be turnedagainst the frictional engagement of the threads with metering bushing 5by force applied to the arm 10 of the blade holder. When latch 32 isdisengaged and latch 27 is engaged, force applied to the arm 10 resultsin rotation of the blade holder about the conical shoulder support 8without movement of the metering post 3.

If the hub portion of blade holder 9 is frictionally tighter to theconical shoulder support 8 than post 3 is to bushing 5, then latch 32 isnot needed.

It has been found that better cutting of a frozen specimen results ifthe cutting blade is cold. To chill the blade as the specimen is beingfrozen, a refrigerant discharge channel 35 is provided in basel,'leading from well 22 to the top of the base at the edge of freezingstage 20. A shallow cavity 36 is provided under the middle portion ofblade 11 into which refrigerant may flow after being discharged fromchannel 35 if the blade holder is placed in position immediately overthe outlet of channel 35 as is indicated in FIG. 4. The carbon dioxidesnow which tends to pack into the cavity keeps the blade cold for alimited period of time. Channel 35 may be plugged, as by a plasticscrew, to limit discharge of refrigerant to the channel 36.

The use of the microtome for sectioning specimens embedded in paraffinand specimens of material that are sufficiently rigid to be cut withoutfreezing will be understood from the foregoing. The block of paraffincontaining the specimen is rigidly mounted in cavity 17 by means of setscrews 18 and slices of the desired thickness may then be cut from thetop of the specimen following procedures as described.

As the drawing shows, blade 11 is sharpened by grinding on one sideonly. This makes it possible to set the microtome to cut at either oftwo angles depending on whether the blade is in the position shown inFIG. 4 or that shown in FIG. 8. Certain materials are more easily slicedat one angle than the other. Also, the blade is so positioned on theblade holder that the edge slices the specimen at the optimum cuttingangle of 60.

The microtome unit may be more or less permanently mounted to a table orbench top by means of screws passing through holes 37. If portability isdesired, a C" clamp 38 having an arm adapted to pass through ahorizontal hole 39 in the base of the microtome unit (FIG. 1) maybeemployed.

An alternate form of cutting head construction is shown in FIG. 9. Thehub of the blade holder 91: is provided with a cylindrical bearingsurface 40 which engages the surface of meteringpost 3. A leaf spring 41is provided to hold the blade holder 92 snugly to the metering post onthe side from which arm extends. The blade holder is mounted upon post 3by means of a spider spring washer 42 which rests upon the annular topof the hub of the blade holder and a screw 43 which threads into the topof the post and has a conical shoulder 44. The screw is turned insufficiently to provide the desired friction pressure between shoulder44 and washer 42 and between the bottom of the blade holder and meteringwheel 6. This construction is somewhat less expensive to manufacturethan that shown in FIG. 3.

ACHIEVEMENT The microtome of this invention provides, in a simple andportable unit, full facilities to prepare a specimen for cutting and toprepare sections of the specimen suitable for microscopic examination. Ahighly versatile instrument, it will produce sections over a wide rangeof thicknesses with only simple metering adjustments. The blade may bebrought to initial cutting position rapidly and, if desired, serialsections may be taken without readjustment between cuts. A choice ofcutting angles is provided and clean and easy cutting is assured by theslicing action resulting from the angle of the cutting edge to theradius of the cutting head. The cutting action is further enhanced bythe cooling of the blade. The specimen is held in frozen condition formore than enough time to complete the sectioning operation. Paraffinembedded specimens may be handled by the unit and no maintenance isrequired except sharpening of the blade, which-is stroppable, orreplacement of the blade.

I claim: 1

1. Microtome apparatus comprising a base; means in said base for holdinga specimen in position for sectioning; and a cutting head assemblymounted upon said base; said assembly comprising a vertical meteringpost mounted by screw threads in said base, a cutting blade holderincluding a substantially horizontal arm supported from a hub upon saidpost for rotation about the axis of said post. an inclined cutting bladesecured to said arm in position to cut a slice from a specimen held uponsaid base when said arm is passed thereover with rotation of saidcutting head assembly, said cutting blade holder being frictionallysupported upon said metering post whereby said holder may be rotatedabout the axis of said post either with or independently of said post,said metering post being provided with a conical shoulder and theinterior of the hub portion of said blade holder being correspondinglyconical whereby said holder is frictionally supported upon said post atthe engaging respective conical surfaces, and adjustable spring mcansarranged to adjust the pressure of the conical surface intercngagementand thus the force re quired to move the blade holder and metering postrelative to each other.

2. Microtome apparatus comprising a base; means in said base for holdinga specimen in position for sectioning; and a cutting head assemblymounted upon said base; said assembly comprising a vertical meteringpost mounted by screw threads in said base, a cutting blade holderincluding a substantially horizontal arm supported from a hub upon saidpost for rotation about the axis of said post, an inclined cutting bladesecured to said arm in position to cut a slice from a specimen held uponsaid base when said arm is passed thereover with rotation of saidcutting head assembly, said cutting blade holder being frictionallysupported upon said metering post whereby said holder may be rotatedabout the axis of said post either with or independently of said post, ametering wheel upon and fixed to said metering post above said microtomebase, the hub portion of the blade holder having an axial bore thereinsnugly engaging the metering post, and means for clamping said hubportion of said holder with adjustable friction engagement against thetop surface of said wheel for rotation either therewith or independentlythereof.

3. Microtome apparatus comprising a base; means in said base for holdinga specimen in position for sectioning; and a cutting head assemblymounted upon said base; said assembly comprising a vertical meteringpost mounted by screw threads in said base, a cutting blade holderincluding a substantially horizontal arm supported from a hub upon saidpost for rotation about the axis of said post, an inclined cutting bladesecured to said arm in position to cut a slice from a specimen held uponsaid base when said arm is passed thereover with rotation of saidcutting head assembly, said cutting blade holder being frictionallysupported upon said metering post whereby said holder may be rotatedabout the axis of said post either with or independently of said post, ametering wheel upon and fixed to said metering post, said metering wheelbeing provided with spaced notches around its periphery, and a latchoperatively mounted upon the hub of the blade holder for engagement witha selected one of said notches to hold said blade holder inpredetermined fixed position relative to said metering wheel and thus tothe metering post.

4. Microtome apparatus comprising a base; means in said base for holdinga specimen in position for sectioning; and a cutting head assemblymounted upon said base; said assembly comprising a vertical meteringpost mounted by screw threads in said base, a cutting blade holderincluding a substantially horizontal arm supported upon said post forrotation about the axis of said post, an inclined cutting blade securedto said arm in position to cut a slice from a specimen held upon saidbase when said arm is passed thereover with rotation of said cuttinghead assembly, a longitudinally slotted threaded bushing mounted invertical position in the microtome base, said metering; post beingscrewed into said bushing, and a set screw provided in said base to bearagainst said bushing to adjust the pressure between the intcrengagingscrew threads and thus the force required to turn said post relative tosaid bushing.

5. Microtome apparatus comprising an elongated base; a cavity in saidbase at one end thereof opening upwardly to receive a paraffin embeddedspecimen therein and means for clamping said specimen in position forsectioning; a freezing stage mounted in the other end of said baseadapted to be cooled by the application of refrigerant thereto to freezea specimen upon and to said freezing stage for sectioning; a cuttinghead assembly mounted upon said base; said assembly comprising avertical metering post mounted by screw threads in said base. a cuttingblade holder including a substantially horizontal arm carrying a cuttingblade or independently of said post; and means for holding said meteringpost in predetermined fixed position relative to said microtomc base.

1. Microtome apparatus comprising a base; means in said base for holdinga specimen in position for sectioning; and a cutting head assemblymounted upon said base; said assembly comprising a vertical meteringpost mounted by screw threads in said base, a cutting blade holderincluding a substantially horizontal arm supported from a hub upon saidpost for rotation about the axis of said post, an inclined cutting bladesecured to said arm in position to cut a slice from a specimen held uponsaid base when said arm is passed thereover with rotation of saidcutting head assembly, said cutting blade holder being frictionallysupported upon said metering post whereby said holder may be rotatedabout the axis of said post either with or independently of said post,said metering post being provided with a conical shoulder and theinterior of the hub portion of said blade holder being correspondinglyconical whereby said holder is frictionally supported upon said post atthe engaging respective conical surfaces, and adjustable spring meansarranged to adjust the pressure of the conical surface interengagementand thus the force required to move the blade holder and metering postrelative to each other.
 2. Microtome apparatus comprising a base; meansin said base for holding a specimen in position for sectioning; and acutting head assembly mounted upon said base; said assembly comprising avertical metering post mounted by screw threads in said base, a cuttingblade holder including a substantially horizontal arm supported from ahub upon said post for rotation about the axis of said post, an inclinedcutting blade secured to said arm in position to cut a slice from aspecimen held upon said base when said arm is passed thereover withrotation of said cutting head assembly, said cutting blade holder beingfrictionally supported upon said metering post whereby said holder maybe rotated about the axis of said post either with or independently ofsaid post, a metering wheel upon and fixed to said metering post abovesaid microtome base, the hub portion of the blade holder having an axialbore therein snugly engaging the metering post, and means for clampingsaid hub portion of said holder with adjustable friction engagementagainst the top surface of said wheel for rotation either therewith orindependently thereof.
 3. Microtome apparatus comprising a base; meansin said base for holding a specimen in position for sectioning; and acutting head assembly mounted upon said base; said assembly comprising avertical metering post mounted by screw threads in said base, a cuttingblade holder including a substantially horizontal arm supported from ahub upon said post for rotation about the axis of said post, an inclinedcutting blade secured to said arm in position to cut a slice from aspecimen held upon said base when said arm is passed thereover withrotation of said cutting head assembly, said cutting blade holder beingfrictionally supported upon said metering post whereby said holder maybe rotated about the axis of said post either with or independently ofsaid post, a metering wheel upon and fixed to said metering post, saidmetering wheel being provided with spaced notches around its periphery,and a latch operatively mounted upon the hub of the blade holder forengagement with a selected one of said notches to hold said blade holderin predetermined fixed position relative To said metering wheel and thusto the metering post.
 4. Microtome apparatus comprising a base; means insaid base for holding a specimen in position for sectioning; and acutting head assembly mounted upon said base; said assembly comprising avertical metering post mounted by screw threads in said base, a cuttingblade holder including a substantially horizontal arm supported uponsaid post for rotation about the axis of said post, an inclined cuttingblade secured to said arm in position to cut a slice from a specimenheld upon said base when said arm is passed thereover with rotation ofsaid cutting head assembly, a longitudinally slotted threaded bushingmounted in vertical position in the microtome base, said metering postbeing screwed into said bushing, and a set screw provided in said baseto bear against said bushing to adjust the pressure between theinterengaging screw threads and thus the force required to turn saidpost relative to said bushing.
 5. Microtome apparatus comprising anelongated base; a cavity in said base at one end thereof openingupwardly to receive a paraffin embedded specimen therein and means forclamping said specimen in position for sectioning; a freezing stagemounted in the other end of said base adapted to be cooled by theapplication of refrigerant thereto to freeze a specimen upon and to saidfreezing stage for sectioning; a cutting head assembly mounted upon saidbase; said assembly comprising a vertical metering post mounted by screwthreads in said base, a cutting blade holder including a substantiallyhorizontal arm carrying a cutting blade and supported upon said post forrotation about the axis of said post to pass over said cavity and saidfreezing stage; said cutting blade holder being frictionally supportedupon said metering post whereby said holder may be rotated about theaxis of said post either with or independently of said post; and meansfor holding said metering post in predetermined fixed position relativeto said microtome base.